1. Technical Field
The present invention relates to a method and apparatus for manufacturing magnetic disk drives in general, and in particular to a method and apparatus for protecting read/write transducers during disk drive manufacturing. Still more particularly, the present invention relates to a method and apparatus for protecting magnetic read/write transducers having magnetoresistive read sensors against electrostatic discharge or electrical overstress during disk drive manufacturing and assembly.
2. Description of the Prior Art
Disk drives have been widely accepted as a cost effective form of data storage for a computer system. Within a disk drive, there is a magnetic recording medium, in the form of a disk, and a magnetic read/write transducer, commonly referred to as a read/write head. The read/write head is attached to, or formed integrally, with a slider that is suspended over the disk on a spring-loaded support arm known as an actuator arm. As the disk rotates at an operating speed, the moving air generated by the rotating disk in conjunction with the physical design of the slider operates to lift the read/write head, allowing the read/write head to glide or fly slightly above and over the surface of the disk on a cushion of air, commonly referred to as an air bearing. In other words, the disk rotates at high speed while the read/write head xe2x80x9cfliesxe2x80x9d slightly above the surface of the rotating disk. The flying height of the read/write head over the disk surface, typically only a few microns, is primarily a function of the speed of disk rotation, the aerodynamic properties of the slider, and the force exerted by the spring-loaded actuator arm.
During the manufacturing of disk drives, a major problem encountered by magnetic read/write heads is the build-up of electrostatic charge on various elements of the heads. Electrostatic charge may be produced, for example, by the presence of certain plastic materials during assembly and subsequent handling of the heads. When electrostatic charge builds up, electrostatic discharge (ESD) may then occur across the edge of an insulating layer between magnetic pole tips and adjacent conductive layers that are exposed and positioned adjacent to the transducing gap at the air bearing surface facing the disk.
It is well-known in the art that magnetoresistive (MR) read sensors are typically utilized as read elements for magnetic read/write heads, especially in high-density disk drives. This is because MR read sensors generally provide a higher output signal than inductive read/write heads such that a higher signal-to-noise ratio for the recording channel and a higher areal density of recorded data on the magnetic disk can be achieved. However, when MR read sensors are exposed to ESD or electrical overstress (EOS) (i.e., a voltage or current input larger than the intended voltage or current under normal operating conditions), the MR read sensors tend to be more susceptible to damage than their inductive counterparts because of the relatively small physical sizes of the MR read sensors. For example, an MR read sensor used for extremely high recording densities typically has a cross-section of 100 Angstroms (xc3x85) by 1.0 micrometers (xcexcm) or smaller, and ESD of only a few volts across such a small resistor is sufficient to produce currents capable of severely damaging or destroying the MR read sensor. As a result, various kinds of ESD/EOS damage to MR read sensors have been found to occur during both manufacturing and processing, which poses serious problems in the manufacturing and handling of magnetic read/write heads incorporating MR read sensors. The degree of ESD/EOS damage experienced by an MR read sensor may vary significantly, from degraded head performances to contamination of the air bearing surface or generation of electrical short circuits, to a complete destruction of the MR read sensor via melting and evaporation. But regardless of its severity, such damage is undesirable.
In recent years, the industry has been using focused ion beam (FIB) pole-trim for inductive heads, and the same FIB technique is being pursued for processing MR read sensors. However, MR read sensors are generally very sensitive to the FIB fabrication process, especially during air bearing surface (ABS) patterning and pole tip trimming. In fact, a recent study reveals that FIB operations can severely damage MR read sensors due to ESD/EOS during ABS pole-trims. Consequently, it would be desirable to provide an improved method and apparatus for protecting read/write heads having an MR read sensor during processing and assembly.
In view of the foregoing, it is therefore an object of the present invention to provide an improved method and apparatus for manufacturing magnetic disk drives.
It is another object of the present invention to provide an improved method and apparatus for protecting read/write transducers during disk drive manufacturing.
It is yet another object of the present invention to provide an improved method and apparatus for protecting magnetic read/write transducers having magnetoresistive read sensors against electrostatic discharge or electrical overstress during disk drive manufacturing and assembly.
In accordance with a preferred embodiment of the present invention, a magnetic head assembly is supported on a substrate having a magnetoresistive sensor element disposed in spaced relationship between several magnetic shield elements. Before a focused ion beam fabrication operation, at least a portion of an air bearing surface of the magnetic head assembly is coated with a thin and transparent layer of conductive material. This layer of conductive material is subsequent removed after the focused ion beam fabrication operation.
All objects, features, and advantages of the present invention will become apparent in the following detailed written description.